Cartridge fuse



March 31, 1936. F Q LA MAR 2,036,177 CARTRIDGE FUSE Filed MaICh 28, 1935 Il: dei \\l I"""lllm Mmmm V MMM W.

INVENTOR Patented Mar. 31, 1936 UNITED STATES PATENT OFFICE CARTRIDGE FUSE Application March 28, 1935, Serial No. 13,380

7 Claims.

This invention relates to conductors, particularly to protective devices therefor, and more especially to thermal or fusible protective devices.

A principal object of this invention is the production of a cartridge type electric fuse of such construction that the fusible element thereof may be renewed without the use of tools.

Another object of the invention is the production of a cartridge type electric fuse of such construction that the fusible element thereof, after its rupture by passage of abnormal current, may be released for removal manually by the simple exercise of manual pressure exerted directly upon the fuse-retaining parts between the operators thumb and a cooperating finger, while the device is held in one hand, thus leaving the other hand free for removal of the useless fragments of the expended fuse and also for manipulation of the fresh fuse during its insertion.

A further object of the invention is to provide a fuse of the type specified which not only may be assembled without the use of tools but which desirably may be so constructed that a fuse link may not be replaced by a fresh link of a higher current carrying capacity.

Other objects and advantages will appear as the description of the particular physical embodiment selected to illustrate the invention progresses, and the novel features of the invention will be particularly pointed out in the appended claims.

In describing the invention in detail and the particular physical embodiment selected to illustrate the invention, reference will be had to the accompanying drawing and the several Views thereon, in which like characters of reference designate corresponding parts throughout, and in which:

Figure 1 is a longitudinal sectional view of a renewable cartridge fuse of the knife blade type; Fig. 2 is a cross-sectional View of the device shown by Fig. 1, taken on the plane indicated by the line II-II of Fig. 1, viewed in the direction of the arrows at the ends of the line; Fig. 3 is a similar cross-sectional view, but taken on the line III-III of Fig. 1; Fig. 4 is a view in medial longitudinal section of the operating parts of the device as shown in Fig. l, but with the shell removed, the parts illustrated being shown as disposed atiright angles to the position shown vin Fig. l; Fig. 5 is a plan View of the operating parts shown in Fig. 4, illustrating a position of a fusible element in course of insertion.

The form of knife blade cartridge vtype renewable fuse'selected for illustration and shown in the drawing is substantially conventional and consists generally of a tubular shell l, formed preferably of insulating material; knife blades 2 and 3, formed preferably of copper, one extending outwardly from each end of the member I; and a 5 renewable fusible link 4, formed of metal, connecting the tangs of the knife blade terminals 5 and 6.

Various constructions have been devised for supporting the knife blade terminals, as 5, in association with the tubular casing I, and for closing the ends of the casing so that flames and hot gases generated by the fusion of the fusible link 4, by an abnormal flow of current, may be properly directed and cooled.

In the arrangement shown in the drawing, the knife blades are supported and associated with the tubular casing I by a substantially conventional arrangement. Each end of the tubular casing I has a metallic ferrule thereon, as 'I and 8. Each knife blade, as 2 and 3, has rigidly attached thereto a shoulder member, as 9 and I0. This shoulder member as 9, best shown in Fig. 2, is in the form substantially of a disc, or washer, just fitting within the bore II of a ferrule, as '1, the shoulder member being somewhat flattened at dia-metrically opposite points, as at I2. Beyond the shoulder 9 there is a slotted washer, as at I3, I4, one on each knife blade. Each of these slotted washers has spaced protuberances, as I5, spacing the washers, as I4, slightly from the end of a ferrule as 8.

An internal threaded cap, as I6 and I l, cooperates with each ferrule, as 'I and 8. Each cap has a flange, as i8, which cooperates with the slotted washer, as I3, for forcing that washer against the shoulder as 9 with its protuberances I5 in contact with an end of a ferrule, as '1.

The insulating, spacing or bridge bar 2l) extends from one tank en-d 5 to the other 6. This spacing bar 29 is attached to the tang of each of the knife blades. This is done, preferably, by providing metal saddles, as 2l and 22. These saddles are best made substantially U-shaped as is best shownhin Fig. 2. The saddles, as 2|, are attached, together with the proximate end of bridge bar 2,0, to the adjacent knife blade tang as 5 by any'suitable appropriate means.

It is preferred to use for this attachment a flat-headed plunger or rivet, as 23, having a shank 2,4 passing through an appropriate orifice 25 in the tang end, the reduced end 26 of the rivet being fixe-d within a separately formed rivet head 2l by being upset therein. Surrounding the rivet shank 24 is a coil spring 28, one end of which bears against the under face 29 of the adjacent head of the rivet, while the other end of the spring bears against the bottom of an inverted cupi-shaped socket 30 formed separately from the bridge or spacing bar 20 and passing through said bar and through the saddle 2l and the tang 5, which are respectively suitably apertured to receive the socket, the latter being screwed into, and connecting, the above-mentioned members of the device. The spring 28 is held under compression, and normally tends vto bias the rivet head 21 yieldingly toward the tang 5.

The play of movement of each rivet is, however, sufiicient to permit suilcient clearance between each tang and the coi-acting rivet head 21 to admit a slotted end 3l or 32 of the fusible link member 4 as shown in Figs. l to 5 inclusive, Fig. 5 illustrating the mode of introducing one end 32, after which the link may be swung around to fit the other end 3| into place (see Fig. 1).

In effecting this operation, the thumb of the operator is caused to engage a rivet head as 23, and the operators index nger is engaged with an adjacent part, such as shoulder l 0, after which a suitable pressure with the thumb serves to unseat the rivet head 21 and permit introduction of the slotted end 32 of the link as already described. A similar operation of the other rivet serves to admit the other slotted end 3l of the link when swung into place. When released, the rivets are urged downwardly until the ends 3| and 32 of the link 4 are embraced firmly between vrivet heads 2l and the tangs 5 and 6, forming an efficient mechanical and electrical connection between the knife blades and fusible link.

Although applicant has .described a particular and specific construction which includes a screw threaded socket in the tang end of the knife blade, nevertheless, it is to be understood that other constructions not depending upon a screw threaded socket are not intended to be excluded.

When the link has been ruptured by passage of an abnormal current, the link-end fragments can be quickly released by a similar operation of each rivet manually, and a fresh link can be inserted in the manner already described.

The play of the rivets may desirably be limited in such fashion that the total thickness of the gap left under a rivet head 2l, when at its outermost position, indicated by the dotted line position of the rivet at the right hand side in iFig, 4, is not enough to admit two fuse links of equal capacity, nor even a fuse link of a capacity sufficiently greater than that of any given capacity for which the fuse device has been designed. This safety provision constitutes an important and valuable improvement over those conventional fuse devices in which substitution of linkage having greater than the proper carrying capacity has been possible, with a detrimental effect upon the factor of safety.

From the hereinbefore given description, it will be seen that applicant has provided a knife blade cartridge type renewable fuse which may be assembled and disassembled without the use of any tools whatever, and that the fusible link may be assembled, removed and replaced without the use of any tools, and by exercising only a natural and convenient pressure between the operators thumb and linger; also a construction is provided whereby only a fusible link of proper car- -rying capacity can be inserted in the fuse.

It is to be understood that applicant by illustrating and describing a knife blade fuse does not intend to exclude the use of his new construction in connection with what are known as ferrule type fuses, which have no knife blades.

Although applicant has particularly described one particular' physical embodiment of his invention and explained the principle and mode of operation thereof, nevertheless he vdesires to have it understood that the form selected is merely illustrative but does not exhaust the possible physical embodiments of the idea of means underlying the invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a renewable knife blade cartridge fuse, a pair of electrical terminals supported in spaced apart relation and each comprising a knife blade including a tang having an orifice disposed transversely of the major axis of the fuse structure and a double headed plunger having a shank mounted reciprocably in said orifice, also a spring coiled upon said shank under compression between said tang and one head of said plunger, whereby the other head of said plunger is biased yieldingly toward the opposite face of said tang, said plunger being readily movable, by manual pressure exerted directly against said first mentioned head, transversely of said major axis to form a gap between the second mentioned head and tang to receive the end of a fuse link.

2. A renewable cartridge fuse having the instrumentalities combined and cooperating as set forth in claim 1 and further characterized by having said plunger formed as a rivet, with one of said heads integral with said shank and said other head including a separately formed member united to said shank permanently by an upset portion of the rivet.

3. In a renewable knife blade cartridge fuse, two spaced knife blade tangs each formed with a screw-threaded orifice therein; a cup-shaped socket screwed into said orifice, and a plunger rivet having a shank reciprocable within said socket and having two heads, one adapted to be moved toward and away from a face of said tang, being biased toward the tang by a spring coiled within said socket and bearing against the other head, said latter head extending into position beyond said socket to permit it to be pressed directly by a digit of the operators hand, thereby creating a gap between said first mentioned head and the adjacent surface of said tang, to receive an end of a fusible link for useful employment.

4. In a renewable knife blade cartridge fuse two spaced knife blade tangs each formed with a screw threaded orifice therein; a cup-shaped socket screwed into said orifice, and a plunger rivet having a shank reciprocable within said socket and having two heads, one adapted to be moved toward and away from a face of said tang, being biased toward the tang by a spring coiled within said socket, and bearing against the other head, said latter head extending into position beyond said socket to permit it to be pressed directly by a digit of the operators hand, thereby creating a gap between said first mentioned head and the adjacent surface of said tang, to receive an end of a fusible link for useful employment, and means for limiting the play of said plunger so that said gap will only admit a fuse link of the proper capacity.

5. In a renewable knife blade cartridge fuse, a pair of electrical terminals and a spacing bar supporting said terminals and having two spaced orifices, each terminal comprising a knife blade provided with a shoulder member and with a tang having a threaded orifice adapted to register with one of said space orices, a pair of saddles, each saddle being mounted between one of said tangs and the corresponding end of said spacing bar, a pair of cup-shaped sockets each socket being threaded externally and screwed into one of said threaded tang orices, a pair of double headed plungers, one for each socket and having a shank mounted reciprocably in its socket, and a spring coiled within each socket upon said shank under compression between the bottom of said socket and one head of said plunger, whereby the other head of said plunger is biased yieldingly toward the opposite face of said tang, said plunger being readily movable, by digital pressure exerted by one hand of an operator drectly against said shoulder and rst mentioned head, to form a gap between the second mentioned head and tang to receive the end of a fuse link, leaving the other hand of the operator free to perform other manipulative operations upon said device.

6. In a renewable knife blade cartridge fuse, in combination: a conductor end formed with an orifice therein; a cup-shaped socket attached to said conductor end; a plunger rivet having a shank mounted reciprocably within said socket and having two heads, one adapted to be moved toward and away from a face of said conductor, being biased toward the conductor by a spring coiled within said socket and bearing against the other head, said latter head extending into a position beyond said socket to permit it to be pressed by a digit of the operators hand thereby creating a gap between said first mentioned head and the adjacent surface of said conductor, to receive an end of a fusible link for useful employment.

'7. In a renewable knife blade cartridge fuse, in combination: two spaced knife blade tangs, each formed with an orice therein; a cupshaped socket secured in said orice; a plunger rivet having a shank mounted reciprocably within said socket and having two heads, one adapted to be moved toward and away from a face of said tang, being biased toward the conductor by a spring coiled within the said socket and bearing against the other head, said latter head extending into a position beyond said socket to permit it to be pressed by a digit of the operators hand thereby creating a gap between said first mentioned head and the adjacent surface of said tang, to receive an end of a fusible link for useful employment.

FRANK C. LA MAR. 

